1. Field of the Invention
The subject invention relates to electronic pressure sensing and signal conditioning applied to automotive engine oil pressure instrumentation.
2. Prior Art
The typical automotive oil pressure sensor is a mechanically intensive device with many moving parts. An example of such a device is a mechanical diaphragm transducer with magnetic or bi-metallic needle movement. The diaphragm expands under pressure, thus displacing the wiper of the potentiometer and providing a variable resistance with respect to pressure. The potentiometer is an integral part of the movements' electrical circuit.
The problem is that such devices provide an unreliable and inaccurate engine oil pressure sensing means. Further, a mechanical potentiometer provides a poor signal for microcomputer controlled instrumentation, ignition and fuel control systems. In addition, these devices are not satisfactory for the rugged automotive under-hood environment and are not designed for high-volume, low-cost production.
Others have attempted various solutions to the above problems. One example is U.S. Pat. No. 4,590,400 to Shukla et al. which discloses a piezoelectic cylinder pressure transmitter.
U.S. Pat. No. 4,163,964 to De Fillippis discloses a pneumatic or hydraulic pressure sensors with several thresholds of response.
U.S. Pat. No. 4,320,664 to Rehn et al. discloses a thermally compensated silicon pressure sensor.
U.S. Pat. No. 4,567,395 to Pundarika discloses a peizoelectric pressure transmitter for an internal combustion engine.
U.S. Pat. No. 4,570,097 to Shukla et al. discloses electrical connections for a piezoelectric pressure transmitter for an internal combustion engine.
U.S. Pat. No. 4,620,438 to Howng discloses a cylinder pressure transmitter for an internal combustion engine.
U.S. Pat. No. 4,616,114 to Strasser discloses a pressure responsive switch having little or no differential between actuation release pressure levels.
U.S. Pat. No. 4,633,579 to Strasser discloses a method for making a pressure responsive switch.
U.S. Pat. No. 4,645,965 to Paganelli discloses a cylinder pressure transmitter for an internal combustion engine.